SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c8a90dc56beee654d31bb8b9476e762894295dd7f665940d1feb52fc4934f191' 
  AND token = '3m35T+HDZ8EntnssjT6RCX23zsxJpMkgw6+bboRMrac=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}